1. Field of the Invention
The present invention relates to an electron-emitting device and an image forming apparatus such as a display apparatus using the electron-emitting device as an electron source, and more particularly to discharge suppression of a surface conduction electron-emitting device.
2. Related Background Art
Up to now, there have been known two types of electron-emitting devices, a thermoelectron type and a cold cathode type. Of these, the cold cathode type includes a field emission type device (FE device), a metal/insulating layer/metal type device (MIM device), a surface conduction electron-emitting device (SCE device), and the like.
The SCE device includes an electron-emitting device in which an electroconductive film having a fissure is connected to a pair of opposing electrodes arranged on a substrate. The electron-emitting device is realized by utilizing a phenomenon that: energization processing called forming is previously conducted to the electroconductive film to be locally broken, deformed, or altered, thereby forming an electrically high-resistance portion having a fissure; then, a voltage is applied between device electrodes to make a current parallel to the surface of the electroconductive film flow; and thus, electron emission occurs from the fissure and/or an electron-emitting portion in the periphery thereof.
As to documents of the prior art relating to the above, device formation in which an electroconductive film is formed using an ink jet apparatus is described in detail in JP 09-102271 A and JP 2000-251665 A, and an example in which the above-mentioned devices are arranged in a XY matrix shape is described in detail in JP 64-031332 A, JP 07-326311 A, and the like. Further, a wiring formation method is described in detail in JP 08-185818 A and JP 09-050757 A, and a driving method is described in detail in JP 06-342636 A and the like.
The electron-emitting portion of the above-mentioned electron-emitting device is arranged at the electrically high-resistance portion including the fissure as described above, and a film containing carbon as a main ingredient is preferably formed at an end portion of the electroconductive film facing the fissure in order to raise efficiency of electron emission.
A process of forming the film containing carbon as a main ingredient is called an activation process. The activation process can be conducted, for example, by repeating application of a pulse between a pair of device electrodes under an atmosphere containing gas comprised of an organic substance. The surface conduction electron-emitting device obtained through the above is disclosed in, for example, JP 09-298029 A.
The above-mentioned electron-emitting device is greatly expected as an electron-emitting device with high efficiency. However, since the electron-emitting portion is formed by energization processing in forming, there is a large variation in the form of the fissure portion. In particular, there occurs a discharge phenomenon of a device which derives from nonuniformity of a fissure width, and thus, there has been a situation in which the manufacture of the electron-emitting device with high reliability is difficult to be conducted.
There will be described below the discharge phenomenon of a device which derives from nonuniformity of a fissure width of the electroconductive film.
FIGS. 13A and 13B are enlarged diagrams (conceptual diagrams) each showing an electron-emitting portion. FIG. 13A is a schematic diagram of a fissure portion after a forming process, and FIG. 13B is a schematic diagram of a fissure portion (a fissure of the electroconductive film and a gap of a film containing carbon as a main ingredient) after an activation process. In each of the figures, the upper part is a plan view, and the lower part is a sectional view.
As described above, as to the formation of the electron-emitting portion, first, energization is conducted to the electroconductive film in the forming process (FIG. 13A), and further, the film containing carbon as a main ingredient is formed at the end portion of the electroconductive film facing the fissure in the activation process. At this time, it is expected that heat generation at several hundreds to one thousand degrees is developed in the fissure portion, and simultaneously with the deposition of carbon, there occurs variation of the fissure position of the electroconductive film due to deformation or evaporation of the electroconductive film (FIG. 13B).
FIG. 13B is an enlarged diagram of the portion with a fissure width of 10 to 100 nm and the whole size of approximately 1 μm or less. However, the size of the actual electroconductive film is generally several tens to several hundreds of μm.
Further, in terms of the display device, several thousands to several millions of devices are provided.
The fissure formation by energization is conducted in the forming process as described above. Thus, in addition to the form shown in FIG. 13B, there may be a case shown in FIG. 14 where there are formed a portion with a wide width, an island-shape remainder material of the fissure, and a portion that branches out from the main line of the fissure. Even if deposition of the film containing carbon as a main ingredient is conducted to the electroconductive film in such a fissure state in the activation process, the island-shape remainder material and the branched portion are left as they are without being largely changed in shape.
In the study made by the present inventors, the discharge phenomenon in electron emission is easily to occur in the above-mentioned electron-emitting device, and the upper limit of the voltage capable of being applied in activation is lowered. Further, also in the case where after the subsequent stabilization process such as vacuum heating, the electron-emitting device is driven in a vacuum envelope, the upper limit of the voltage for driving without discharge is lowered. Thus, a desired electron emission current cannot be obtained. Alternatively, in the case where the voltage with which the desired electron emission current can be obtained is continuously applied, a device discharge may be caused, and thus, the electron-emitting device may be broken.